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Editor's note: A previous version of this article incorrectly stated that the FDA has never approved an inhalable insulin therapy. The Fool regrets the error.

With the SPDR S&P Biotech Index up 32% year to date, it's evident that investment dollars are willingly flowing into the biotech sector. Keeping that in mind, let's have a look at some of the rulings, studies, and companies that made waves in the sector last week.

As you might imagine, Christmas week wasn't filled with an overabundance of rulings and data, but there were still quite a few big events that investors should have taken note of. Here are four that crossed my radar, in case you missed them.

The biggest news this week was an approval in Japan for next-generation blood-thinning drug Eliquis in Japan. The drug, developed by Bristol-Myers Squibb and Pfizer , has now been approved in Canada, the European Union, and Japan over just the past few weeks, but is awaiting a decision from the Food and Drug Administration, which sent the company a rejection letter earlier this year demanding more clinical data. Both companies have resubmitted their new drug application, with a PDUFA date of March 17. Although it isn't approved in the United States yet, I've proclaimed Eliquis to be a life-changing drug and figure it could be the blockbuster that both Bristol and Pfizer have been seeking since Plavix and Lipitor went off patent.

Roche also received a nice bit of good news this week, when the FDA expanded the indication for oseltamivir, better known as Tamiflu, to children as young as 2 weeks old and up to 12 months old as a new symptom flu treatment. The FDA was very clear that Tamiflu is not a flu preventative agent for this age group and fully encouraged everyone older than 6 months of age to get an annual influenza shot, but this added indication could help boost Tamiflu's sales, which have struggled recently.

In less dramatic but nonetheless important news, AMAG Pharmaceuticals filed for a supplemental new drug application for its iron-deficiency anemia, or IDA, drug, Feraheme. AMAG hopes to expand Feraheme's indication from just chronic kidney disease, or CKD, to all iron-deficient anemias. CKD affects approximately 1.6 million people in the U.S., with an additional 2.4 million affected by a non-CKD form of IDA. Given that sales of Feraheme have stalled, this additional indication could more than double sales. In advance of its supplemental NDA, AMAG has run two late-stage trials encompassing more than 1,400 patients and should receive a decision sometime next year.

Finally, MannKind's massively dilutive offering, which I alluded to back in early October, finally came to fruition, with a twist. MannKind's outstanding share count did increase by 200 million to 550 million; however, 40 million shares were sold to the Mann Group, which is controlled by MannKind's CEO, Alfred Mann. In short, MannKind's CEO purchased $107 million more worth of MannKind's stock. If that's not an indication of commitment by a CEO, I'm not sure what is. Investors will definitely be glad to see this development, as history isn't on their side. MannKind's lead drug, an inhalable insulin to treat type 1 and type 2 diabetes, known as Afreeza, is going up against figures that show the FDA has approved inhalable insulin therapies only in rare cases. Needless to say, 2013 should be a make-or-break year for MannKind.

Is 2013 the year MannKind turns it around?Still down around 90% from its highs less than a decade ago, there's been no giant leap for MannKind shareholders. The debate rages over whether the company's revolutionary inhalable insulin, slated to go in front of the FDA next year, will be a complete flop or a massive blockbuster success. In this brand-new premium report on MannKind, we outline every key topic investors have to know with this risky stock. It also comes with a full year of analyst updates to keep you covered as key news develops, so don't miss out -- simply click here now to claim your copy today.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.